Corrosion-resistant article and method of making the same



Nov. 30 1926. 1,608,694

J. R. CAIN CORROSION RESISTANT ARTICLE AND METHOD OF MAKING THE SAME Filed August 10, 1925 VIII/III/III/I/IMI/II/IIIMI E 1 KZW J2 less J'eel I (Zrwzzzam J'fainless J'zeel 7 5 3 gwuentov alimmq Patented Nov. 30, 1926.

JOHN 3. GAIN, OF WABHINGTQN, OI COLUMBIA.

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Application ma August 10.1925. Serial m. 49,867.

This invention relates to a corrosion resistant article and method of making the same. V

The primary object of the'present invention is the provision of an article of manufacture having 'far greater rust or corrosion resistant 'roperties than similar articles known at t e present day.

Articles of manufacture of the' present day, known as stainless or rustless steel and iron, are alloys, having as their essential constituents ten to sixteen percent chromium alloyed with iron, the latter usually containing a few tenths to one or two percent of impurities such as copper, carbon, manganese, sulphur and phosphorus.

It is well known in the art that the corrosion resistant properties of stainless steel or iron may be increased by adding more chromium to the alloy to the extent of be yond sixteen percent; however, such large additions of chromium not only increase the cost of production, but introduce manufacturin problems, such as extreme diiiiculty inro ing and forging; stiffness and proneness to brittleness of ob'ects fabricated from sheets of the metal bydrawing or pressing; difficulties in ickling, and the like. It will be obvious, terefore, that the known superiority of high chrome irons and steels, particularly as to the corrosion resistant properties thereof, cannot be utilized to any great commercial extent.

Further, it is well known in the art that stainless irons and steels are very apt to corrode to a great extent in the atmosphere or in soil or water unlessthey are pro erly anneeded and pickled by special an unusual processes, and this is true to such an extent that unless the surface scale is completely removed after annealin stainless or rustless irons and steels corro e superficially to substantially the same extent as the usual and ordinary steel and iron.

, It is obvious that resistance to corrosion or resistance to oxidization at high temperatures are surface phenomena, for oxy en can initially act only on the surface 0 a metal to cause it to scale at high temperatures, or water and oxygen can corrode the metal initially only at the surface at ordinag temperatures.

onsidering the above, it is the primary object of the present invention to lmprove the surface of stainless iron or steel, or other corrosion resistant metal.

v A further'object of the present invention is the provision of an article of manufacture having a body portion or base, of corrosion resistant metal.

A still further object of this invention 7 is the provis ion of a method of making a corroslon resistant article.

Another object of this invention is the provision of an article of manufacture having a surface of corrosion resistant metal.

Another object of the present invention is the provision of an article of manufacture having a body or base portion of corrosion resistant metal, the same being covered or coated with a metal having extreme corrosion resistant pro erties.

Other objects an advantages of this invention will be apparent from the following description, taken in conjunction with the accompanying drawings, in which:

Figure 1 illustrates one form of the invention wherein a sheet of stainless steel or iron or other corrosion resistant metal is coated on one side with chromium.

Fig. 2 is a similar View showing another form of the invention wherein a sheet of stainless steel or iron or other corrosion resistant metal is coated on both sides with chromium, and

Fig. 3 is a view, similar to Fig. 1 wherein the coated stainless steel or iron or other corrosion resistant metal has been subjected to a subsequent annealing operation.

Referrin now more particularly to the drawings, 1n which similar' characters of reference designate similar parts in the several views, the numeral 1 indicates a bod portion, or what may be termed a base meta which is formed of an alloy of iron and chromium or corrosion resisting steel. The particular constituents of this base metal 1 will be hereinafter described. In Fig. 1 the base metal is coated on one side with chromium indicated at 2, while in'Fig 2 the base 1 is coated on both sides with chromium, also indicated at 2. In Fig. 3, the base 1 is coated on one side with chromium 2, and subsequent tosuch coating, the coated base is subjected to an annealin operation, the result being that the coate base becomes really alloyed with the chromium of the coating to a certain extent, as indicated by the irregular juncture line 3.

In the manufacture of the article of the present invention, I first form a base, shown at 1, by alloyingchromium with iron to the extent of six to sixteen percent. This amount of chromium has been found satisfactory in practice, but obviously, greater amounts may be used if desired.

The alloyed metal is then annealed, the same being commonly known, when containing ten to sixteen percent chromium, as stainless steel or stainless iron. This annealed alloy is then pickled by pickling methods such as are usually employed for ordinary irons or steels. Such ordinary methods of pickling are readily adaptable to this process or method, provided the stainless steel or iron, or alloy base metal 1 has been properly annealed. I preferably use the sulphuric acid type of pickling bath, although obviously, other types of baths may be utilized with success.

As a modification, the base metal 1 may be pickled electrolytically, but in any case it is desirable to pickle the base metal in a bath such that any chromium dis:olved from the base metal may accumulate in the bath as a source of the whole or part of the chromium used subsequently for coating the base metal 1.

The base metal 1 having been pickled, I next coat the same with chromium. Obviously there are many ways of accomplishing this, but as an example, the base metal 1 may be electroplated by suitable means; the electroplating bath utilizing the chromium recovered from the pickling bath, in forms suitable for chromium sulphate, chrome alum, or chromic acid plating baths.

The thickness of the chromium coating may be varied to suit various requirements. Further, it willbe apparent that methods other than the electrolytic method for applying the chromium, may be used; for example, the chromium may be applied by thermal decomposition under suitable conditions, of chromium chloride or other halides of chromium.

Referring now to Fig. 3; as an additional step in the method heretofore described, the coated metalis subjected to a further annealing operation which drives the coating metal into the coated metal, as shown bythe reference character 3, .so that, to a certain extent, the coated metal, or base 1 becomes alloyed with the coating metal 2. It will .be obvious that by suitably proportioning the thickne"s of the coating metal 2 relative to that of the base metal 1, the above mentioned beneficial effects of ,high

'chrome alloys may be obtained throughout the entire cross section of the coated metal by such alloying annealing.

From the above description it is believed that the invention will be fully apparent to those skilled in the art. It will be apparent that as a corrosion protector, this coatin applied to the particular type of base meta described is-unique, for not only is the underlying metal coated with a metal which closely resembles the so-called noble metals,

such as gold, silver and platinum in its insolubility and inalterability, but also, since the difference in electrolytic potential between the coating 2 and the base or underlying metal 1 is extremely slight, there is little tendency for either metal to corrode by electrolytic corrosion because of accidental defects in the coating such as pin holes, scratches or the like.

Throughout the specification the term corrosion resistant has been employed and it is well known that many metals are resistant to corrosion resulting from certain conditions. In this invention it is not. to be assumed that the article is resistant to all kinds of corrosion or that it will withstand corrosion by every known corrosion producing element or condition. It is well known that silver is, corrosion resistant to certain media but it is also a 'fact that silver is not corrosion re.:istant to certain media which do not attack chromium. 'For example, silver oxidizes at 200 C. whereas chromium when exposed to the air for a number of Weeks shows no corrosion; silver decomposes in steam whereas chromium is unaffected by steam even after being subjected to the action thereof for a period of about a year;

chromium is unaffected by water; nitric acid is a rolvent for silver whereas chromium is unsoluble in nitric acid; in the presence of air, fused alkali hydroxides readily attack silver whereas chromium is not attacked by alkalis; in the presence of air, silver dissolves in ammonia whereaschromium plated articles exposed to air show no loss of weight, therefore, it is obvious that chromium is corrosion resistant tof ammonia; air and sodium chloride solution act very rapidly on silver and a concentrated solution of sodium chloride dissolves silver very rapidly whereas chromium is only very slightly attacked after a months exposure to a spray of sodium chloride solution; hydrogen sulphide tarnishes silver especially if small amounts of air or moisture are present whereas chromium plated samples exposed to air carrying sulphur dioxide show a slight gain instead of a lo?s. The above examples are cited to more readily define the meaning of the term corrosion resistant but in general it may be stated that the article of the pres- ,ent invention is corrosion resistant to the usual atmospheric conditions, salt water, salt air, and is especially adapted for use in the customary and usual domestic cooking vessels and other vessels and for purposes for which silver is totally unsuitedlbecause of the corrosion resistant properties and the hardnessof chromium and also because of the comparative cheapness of chromium as compared to the high cost of silver. Having thus described the invention, what I claim as new and desire to secure by Letters Patent of the United States, is

1. An article of manufacture comprising abase metal of the kind known as stainless steel or i'ron'having a corrosion resistant coating possessing the properties of chromium.

2. An article of manufacture comprising a base metal of the kind known as stainless steel or iron having a coating of chromium. 3. An article of manufacture comprising a base metal formed of an alloy of iron and chromium, and having a corrosion resistant coating possessing the properties of chromium. p l i 4. An article of manufacture comprising a base metal formed of an allov of iron and chromium, and having a coating of chro mium.

5. An article of manufacture comprising a base metal having six to nine percent chromium, said base metal having a coating of chromium.

6. An article of manufacture comprising a base metal having from siX to nine percent of chromiun'i, said base metal having a cor rosion resistant coating possessing the properties of chromium.

7. An article of manut'iwture, comprising a base metal formed oi an alloy of iron and chromium to the extentotsix to nine percent and having a corroson resistant coating possessing the properties of chromium.

8. An article of manufacture comprising a base metal formed of an alloy of iron and chromium to an extent of about six per cent and having a coating of chromium.

9. An article of manufacture comprising a base metal formed of an allov of iron and chromium to the extent of six to nine percent and having a coating of chromium.

10. The method of making corrosion resistant articles which comprises forming an.

alloy of iron and chromium, annealing and pickling said alloyed metal and then coating the alloyed metal with a metal possessing the properties of chromium.

11. The method of making corrosion resistant articles which comprises coating stainless steel or iron with chromium.

12. The method of making corrosion resistant articles which comprises forming. an alloy of iron and six to nine percent of chromium, annealing and removing the scale from said alloy and then coating the alloyed metal with a corrosion resistant metal possessing the properties of chromium.

13. The method of making corrosion resistantarticles which comprises forming a ',.corrosion resistant alloy, annealing and pickling said alloy, and then coating said alloy with a corrosion resistant metal possessing the properties of chromium.

14. The method of making corrosion resistant articles which comprises forming an alloy of iron and six to nine percent of chromium, annealing and removing the scale from said alloy ,.and then coating said alloy with chromium.

15. The method of making corrosion resistant articles which comprises forming an alloy of iron and chromium, annealing and pickling said. alloy, and then electroplating said pickled alloy with chromium.

16. The method of makingcorrosion resistant articles which comprises forming an alloy of iron and chromium, annealing and pickling said alloy, electroplating said pickled alloy with chromium, and then annealing the electroplated article to alloy a portion of the electroplated coating with the first named alloy.

17. The method of making corrosion resistant articles which comprises forming a base of iron and six tonine percent chromium, annealing and pickling said base, coating said base with chromium, and then annealing said coated article to drive a portion of the chromium into said base.

18. The method of making corrosion resistant articles which comprises pickling an alloy of iron and chromium in a bath of such a character as to dissolve chromium, and then coating the pickled alloy with chromium recovered from said pickling bath.

19. The method of making corrosion resistant articles which comprises pickling an annealed alloy of iron and chromium in a bath to remove the scale therefrom and to dissolve chromium, recovering the chro- :mium from the bath, and then electroplating the pickled alloy with such recovered chromium.

'20. An article of manufacture comprising a base metal formed of an alloy including iron and chromium and having a corrosion resisting coating possessing the properties of chromium.

'21. An article of manufacture comprising a base metal formed of an allov including iron and chromium and having a coating of chromium.

22. An article of manufacture comprising a base metal formed of an alloy including iron and chromium and having a coating possessing the properties of chromium.

In testimony whereof I hereby aflix mv signature.

JOHN a. cam. 

